WO 2006/039809 A1 discloses a computed tomography apparatus being adapted for reducing metal artifacts in a reconstructed image. Projection data are acquired by a detection unit, while a radiation source and the detection unit move along a helical trajectory relative to a patient. A reconstruction unit reconstructs an image of the patient from the acquired projection data and an artifact creating object is determined in this reconstructed image, which can be regarded as a preliminary image. The determined artifact creating object is forward projected onto the detection unit and projection data located within the forward projected artifact creating object are replaced by replacement data, which are calculated by interpolating over projection data outside of the forward projected artifact creating object, thereby producing modified projection data. The modified projection data are used for reconstructing a final image of the patient.
The use of such a computed tomography apparatus has the drawback that the modified projection data are still different to projection data, which would have been measured without the artifact creating object located within the patient, i.e. the modified projection data are still corrupted and produce therefore still artifacts in the final reconstructed image.